You are here:

I have a Windows 2008 / VMware server running a couple of instances of Turnkey. Would it be more efficient to run one instance and install the other apps (ex> drupal, wordpress, joomla) then to have a separate instance for each. I try to keep the memory low for each around 128mb.

Installing and maintaining multiple appliances is going to be easier than setting up and maintaining one big appliance. You'll also get less security isolation so if one of your applications suffers from a security breach, you'll get less protection if all the applications are installed on one VM.

OTOH, if all applications are on the same server there is only one copy of the OS to maintain and you're going to use resources such as memory more efficiently. It usually doesn't matter nowadays for most usage scenarios though.

You can easily add web apps to a Turnkey appliance the same way you would any other Apache server on Ubuntu. However if you are not comfortable downloading and installling the files and setting up the database (which isn't very hard), and maybe configuring multiple virtual hosts, then multiple appliances may be easier. Having them all on a single vm would definitely be more efficient. Instead of three running 128mb each, you could do it all on one with 256mb.